4,132 research outputs found
Study of Apollo water impact. Volume 9 - Mode shapes and natural frequencies analysis Final report
Numerical analysis on vibrational modes and frequencies in Apollo water impac
2D Superconductivity: Classification of Universality Classes by Infinite Symmetry
I consider superconducting condensates which become incompressible in the
infinite gap limit. Classical 2D incompressible fluids possess the dynamical
symmetry of area-preserving diffeomorphisms. I show that the corresponding
infinite dynamical symmetry of 2D superconducting fluids is the coset
, with
the chiral algebra of quantum area-preserving diffeomorphisms
and I derive its minimal models. These define a discrete set of 2D
superconductivity universality classes which fall into two main categories:
conventional superconductors with their vortex excitations and unconventional
superconductors. These are characterized by a broken symmetry and are labeled by an integer level . They
possess neutral spinon excitations of fractional spin and statistics which carry also an isospin
quantum number; this hidden symmetry implies that these anyon
excitations are non-Abelian. The simplest unconventional superconductor is
realized for : in this case the spinon excitations are semions
(half-fermions). My results show that spin-charge separation in 2D
superconductivity is a universal consequence of the infinite symmetry of the
ground state. This infinite symmetry and its superselection rules realize a
quantum protectorate in which the neutral spinons can survive even as soft
modes on a rigid, spinless charge condensate.Comment: Revised version to appear in Nuclear Physics
Classification of Quantum Hall Universality Classes by $\ W_{1+\infty}\ $ symmetry
We show how two-dimensional incompressible quantum fluids and their
excitations can be viewed as edge conformal field theories,
thereby providing an algebraic characterization of incompressibility. The
Kac-Radul representation theory of the algebra leads then to
a purely algebraic complete classification of hierarchical quantum Hall states,
which encompasses all measured fractions. Spin-polarized electrons in
single-layer devices can only have Abelian anyon excitations.Comment: 11 pages, RevTeX 3.0, MPI-Ph/93-75 DFTT 65/9
A Unified Conformal Field Theory Description of Paired Quantum Hall States
The wave functions of the Haldane-Rezayi paired Hall state have been
previously described by a non-unitary conformal field theory with central
charge c=-2. Moreover, a relation with the c=1 unitary Weyl fermion has been
suggested. We construct the complete unitary theory and show that it
consistently describes the edge excitations of the Haldane-Rezayi state.
Actually, we show that the unitary (c=1) and non-unitary (c=-2) theories are
related by a local map between the two sets of fields and by a suitable change
of conjugation. The unitary theory of the Haldane-Rezayi state is found to be
the same as that of the 331 paired Hall state. Furthermore, the analysis of
modular invariant partition functions shows that no alternative unitary
descriptions are possible for the Haldane-Rezayi state within the class of
rational conformal field theories with abelian current algebra. Finally, the
known c=3/2 conformal theory of the Pfaffian state is also obtained from the
331 theory by a reduction of degrees of freedom which can be physically
realized in the double-layer Hall systems.Comment: Latex, 42 pages, 2 figures, 3 tables; minor corrections to text and
reference
On the c-theorem in more than two dimensions
Several pieces of evidence have been recently brought up in favour of the
c-theorem in four and higher dimensions, but a solid proof is still lacking. We
present two basic results which could be useful for this search: i) the values
of the putative c-number for free field theories in any even dimension, which
illustrate some properties of this number; ii) the general form of three-point
function of the stress tensor in four dimensions, which shows some physical
consequences of the c-number and of the other trace-anomaly numbers.Comment: Latex, 7 pages, 1 tabl
Monte--Carlo Thermodynamic Bethe Ansatz
We introduce a Monte--Carlo simulation approach to thermodynamic Bethe ansatz
(TBA). We exemplify the method on one particle integrable models, which include
a free boson and a free fermions systems along with the scaling Lee--Yang model
(SLYM). It is confirmed that the central charges and energies are correct to a
very good precision, typically 0.1% or so. The advantage of the method is that
it enables the calculation of all the dimensions and even the particular
partition function.Comment: 22 pages. Added a footnote and realizations for the minimal models.
Fortran program, mont-s.f90, available from the source lin
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